Intraocular Lens System

ABSTRACT

An intraocular lens system comprising: an anterior light-converging intraocular lens ( 16 ) for positioning within the eye, the anterior lens having an anterior surface and a posterior surface; and a posterior light-diverging intraocular lens ( 17 ) for positioning within the eye posterior to the anterior lens, the posterior lens having an anterior surface and a posterior surface; wherein the posterior lens is separate to the anterior lens; and wherein at least one of the surfaces of the anterior lens or surfaces of the posterior lens is a modified surface which includes a surface aberration which increases the depth of focus of the lens, optimises image quality and may also provide for a magnified image over a range of retinal eccentricities.

FIELD OF THE INVENTION

The present invention relates to an intraocular lens system,particularly to an intraocular lens system comprising an anterior lensand a posterior lens.

BACKGROUND OF THE INVENTION

The most common condition affecting the macula is age-related maculardegeneration (AMD)—this is also the most common cause of significantvisual loss in the developed world. AMD results in loss of thelight-sensitive cells (photoreceptors), and supporting tissue at theback of the eye, in a specialised part of the retina known as themacula. The condition most often involves the very central part of themacula (the fovea), an area which enables reading and the recognition offaces. In the majority of patients with age-related macular degenerationloss of vision occurs over a number of years and the pattern of visualloss allows for the maintenance of small islands of functioningphotoreceptors in the macula. These remaining islands of tissue maypermit sufferers to read but, because the density of light-sensitivecells reduces with increasing eccentricity from the fovea, visualresolution may be impaired such that at 3 degrees nasal to the centralfovea, the visual acuity is reduced to 0.4 (compared with a visualacuity of 1.0 at 0 degrees), and at 5 degrees the visual acuity isfurther reduced to 0.34. Depending on the severity of the disease,patients may benefit from visual aids such as magnifying glasses, or theuse of spectacle-mounted or hand-held telescopic devices that facilitatereading. Use of such devices is often restrictive because magnifyingglasses are not easily portable (and require good lighting), andtelescopic devices can severely reduce a patient's field of view.Despite the problems associated with reduced visual resolution, patientswith age-related macular degeneration and similar conditions affectingthe central visual field may still make effective use of residualmacular tissue outside the damaged fovea (sometimes referred to as the‘preferred retinal locus’ or PRL) although this may require the patientto learn to fixate eccentrically—something that is not always easilyaccomplished. One potential method of improving patients' fixation is toundertake surgery to introduce a device to modify the path of light inthe eye such that images are focused on the PRL with or without amagnifying effect. However, the precise location of the PRL varies frompatient-to-patient and accurate targeting of the PRL using such anapproach is essential if a patient's vision is not to be made worse.Furthermore, as the disease progresses and remaining islands offunctioning retina shrink in size, the location of the PRL can shift andit may become necessary to alter the path of light in the eye to takeaccount of this.

Current surgical approaches to the management of poor vision inage-related macular degeneration include the implantation of telescopiclenses, in some cases not dissimilar to those employed for use incataract surgery. Such lenses have the advantage of superior opticswithout the disadvantages associated with the use of external telescopicdevices. Furthermore, telescopic devices may be configured in such a wayas to provide a magnified image that is focused on an area of healthymacula eccentric to the fovea. Most existing designs for theseintraocular devices adopt variations on a Galilean telescope system suchthat a diverging intraocular lens (IOL) is sited in the eye behind aconverging IOL.

IOLs may be used in cataract surgery to replace the focusing power ofthe natural crystalline lens and may be employed in isolation to providea fixed focal distance or in combination to restore a degree ofaccommodation (the ability to see objects in the distance and close-up).The most commonly used approach is to site a single lens in theposterior chamber of the eye (behind the iris)—IOLs implanted into theposterior chamber of the eye are disclosed in U.S. Pat. Nos. 3,718,870;3,866,249; 3,913,148; 3,925,825; 4,014,049; 4,041,552; 4,053,953; and4,285,072. So-called ‘accommodative’ IOLs are disclosed in U.S. Pat.Nos. 4,254,509; 4,253,199; 4,409,691; 5,674,282; 4,842,601 and WO2008/077795—these typically harness the effects of the ciliary muscle,normally active in deforming the natural crystalline lens, to alter thefocusing power of a single piece IOL or similar arrangement of two ormore implants. These devices differ from intraocular Galilean telescopesin that they do not confer the ability to magnify an image or displaceit from the foveal centre.

A basic paraxial approach to an intraocular Galilean telescope is asfollows:

$\left. \left. \begin{matrix}{D = {f_{obj} + f_{oc}}} \\{M = {- \frac{f_{oc}}{f_{obj}}}}\end{matrix} \right\}\rightarrow\begin{matrix}{f_{obj} = {D\frac{M}{M - 1}}} \\{f_{oc} = {D\frac{- 1}{M - 1}}}\end{matrix} \right\}$

D=distance between lenses (assumed thin lenses)M=magnificationfobj=focal length of the objective lensfoc=focal length of the ocular lens

Galilean intraocular telescopes that employ a light-diverging IOLlocated in the posterior chamber of the eye and a light-converging lensin the anterior chamber of the eye are disclosed by Orzalesi et al.(Ophthalmology Volume 114 Issue 5; 2007) and in U.S. Pat. No.20120136438 A1. These systems provide for magnification of an image andthe deviation of light to target healthy parts of the macula. The latteris achieved by displacement of the diverging lens in a directionperpendicular to the optic axis of the converging lens by means of anasymmetrical haptic design (the haptic is the supporting arm of an IOL,most often seen in pairs with each one attached at opposite sides of theimplant to ensure the position of the IOL in the eye remains stable). Byshortening one haptic and lengthening the other it is possible to shiftthe diverging IOL such that a prismatic effect is achieved and lightfocused eccentric to fixation. The arrangement has a number ofdisadvantages. Firstly, the prismatic effect is conferred by thediverging IOL, which lies behind the converging IOL in both instances,thereby making access difficult for the purpose of rotating thediverging IOL to target the PRL should its location change at a futuredate. Secondly, the siting of an IOL in the anterior chamber is known tobe associated with secondary pathology such as glaucoma and damage tothe cornea of the eye. Thirdly, the optics of such a configuration arehighly dependent on the IOLs remaining a fixed distance apart, for thepurposes of magnification, and at a fixed displacement perpendicular tothe optical axis (in the case of the diverging lens) for the purposes oftargeting the PRL so that without consideration of the optimalconfiguration of the IOLs in relation to one another the system has thepotential to make a patient's vision even worse.

Intraocular telescopes that take advantage of IOLs placed in fixedalignment are disclosed in U.S. Pat. Nos. 7,186,266; 6,596,026;5,391,202; 7,918,886; 20040082995 and 20110153014. The principaldisadvantages of fixing the diverging lens to the converging lens inthese systems are that: 1) The arrangement may not permit thedisplacement of one lens in relation to the other to create theprismatic effect necessary to target the PRL (as is the case with mostcylindrical one-piece designs); 2) in some instances, the prismaticeffect, if achieved, may not be modifiable without replacing theimplant; 3) in the case of systems where the device (or part of thedevice) is implanted in the capsular bag, fibrosis of the capsular bagover the implant may prevent its easy replacement or rotation should theneed arise for adjustment in response to a change in the PRL; 4) thesize of the implant is increased such that a larger incision in the eyeis required to site it (this is associated with longer wound-healingtime and increased astigmatism that may adversely affect the quality ofvision). In addition the high dioptric power of the lenses employedrequires careful consideration of the lens surfaces so as to optimisevisual potential and avoid poor performance of the implant.

Consequently there exists the need for an intraocular telescope that maybe sited through a small incision in the eye and one that provides theadvantages of magnification and the ability to focus an image on thePRL, whilst also being flexible enough to allow for changes in thelocation of the patient's PRL and, critically, ensuring that any imageis tightly focused at the back of the eye.

SUMMARY OF INVENTION

According to a first aspect of the present invention there is providedan intraocular lens system comprising an anterior light-convergingintraocular lens for positioning within the eye, the anterior lenshaving an anterior surface and a posterior surface; and a posteriorlight-diverging intraocular lens for positioning within the eyeposterior to the anterior lens, the posterior lens having an anteriorsurface and a posterior surface; wherein the posterior lens is separateto the anterior lens; and wherein at least one of the surfaces of theanterior lens or surfaces of the posterior lens is a modified surfacewhich includes a surface aberration which increases the depth of focusof the lens.

The surface aberration optimises image quality and may also provide fora magnified image over a range of retinal eccentricities.

The system of two or more intraocular lenses (IOLs) are arranged in themanner of a Galilean telescope to provide a magnified image at, oroutside, the fovea in individuals with poor central vision.

The tolerance of the system is advantageously increased as a result ofthe aberration of the modified surface. This means that the relativepositioning of the two lenses is less critical so the system is lesssensitive to positioning requirements which arise for example due to theanatomy of the eye of the patient.

The system advantageously permits free rotation of the anterior IOLrelative to the posterior IOL, as well as enabling its replacement ifnecessary. This lens configuration also ensures that the path of lightcan be easily modified should macular disease progress.

At least one optic (i.e at least one lens) has at least one asphericalsurface. This optimizes the quality of the image presented to the retinaof the eye. The remaining lens surfaces may be spherical or one or moremay be rendered aspherical to further increase the tolerance of thesystem to errors in IOL positioning. All lens surfaces may be renderedaspherical to further increase the tolerance of the system to errors inIOL positioning.

Throughout this application, the terms “lens” and optic are usedinterchangeably. It should be understood that optic refers to arefractive component of the intraocular lens.

The use of two intraocular lenses (IOLs) for in concert provides a wayto maximize the visual potential of patients with age-related maculardegeneration and other progressive and non-progressive conditions thataffect the macula and central field of vision.

Optionally, the surface aberration includes a spherical aberration.

Optionally, the modified surface is a rotationally symmetric polynomialsurface.

Optionally, the surface aberration includes an aberration of at least4th order.

Optionally, the surface aberration includes an aberration of no morethan 6th order.

Optionally, the surface sag (z coordinate) of the modified surface isgiven by:

$z = {\frac{{cr}^{2}}{1 + \sqrt{1 - {\left( {1 + k} \right)c^{2}r^{2}}}} + {\alpha_{1}r^{2}} + {\alpha_{2}r^{4}} + {\alpha_{3}{r^{6}.}}}$

In this way, the aberration may be any high order aberration(particularly 4th to 6th order); a spherical aberration or otherwisesuch that the tolerance of the IOL system is improved. For example thesystem may induce a spherical aberration up to 0.4 microns of root meansquared for a 4 mm pupil. The IOL system can therefore act to improvethe patient's vision over a range of lens separation distances ratherthan at a specific separation distance. The IOL system avoids problemsassociated with other IOL systems where placement of the system in apatient's eye can actually result in a reduction in quality of thepatient's vision due to optical effects associated with the relativelocations of the two lenses.

In some embodiments the modified surface can be a simple conic surfacewith the surface sag (z) defined only by radius and conic constant.

Optionally, the modified surface includes a second aberration, thesecond aberration being a Zernike polynomial for any one of: tilt,defocus, astigmatism, or coma.

In this way, the IOL system is further optimised to correct foradditional optical aberrations of specific patients.

Preferably, the intraocular lens system comprises a first and a secondmodified surface.

Preferably, both the anterior lens and the posterior lens each include amodified surface.

Preferably, the posterior surface of the anterior lens and the anteriorsurface of the posterior lens are both modified surfaces.

Preferably, the second modified surface includes a surface aberrationwhich increases the depth of focus of the lens.

Preferably, the surface aberration of the second modified surfaceincludes a spherical aberration.

Optionally, the second modified surface is a rotationally symmetricpolynomial surface.

Optionally, the surface aberration of the second modified surfaceincludes an aberration of at least 4^(th) order.

Optionally, the surface aberration of the second modified surfaceincludes an aberration of no more than 6^(th) order.

Optionally, the surface sag (z coordinate) of the second modifiedsurface is given by:

$z = {\frac{{cr}^{2}}{1 + \sqrt{1 - {\left( {1 + k} \right)c^{2}r^{2}}}} + {\alpha_{1}r^{2}} + {\alpha_{2}r^{4}} + {\alpha_{3}r^{6}}}$

In this way, the aberration may be any high order aberration(particularly 4^(th) to 6^(th) order); a spherical aberration orotherwise.

In some embodiments the second modified surface can be a simple conicsurface with the surface sag (z) defined only by radius and conicconstant.

Optionally, the second modified surface includes a second aberration,the second aberration being a Zernike polynomial for any one of: tilt,defocus, astigmatism, or coma. This aberration may be at least a 4^(th)order aberration. Optionally, it may be no more than a 6^(th) orderaberration.

In this way, the IOL system is further optimised to correct foradditional optical aberrations of specific patients.

Optionally all four of the surfaces are modified surfaces to increasethe range of depth of focus thereby increasing the tolerance of thepositioning of the lenses in the eye.

Optionally, the intraocular lens system further includes: an anteriorlens positioning means; and a posterior lens positioning means; whereinthe anterior positioning means is configured such that when the anteriorlens is positioned within the eye, the anterior positioning meanslocates the anterior lens so that it is aligned with the optical axis ofthe eye; and wherein the posterior positioning means is configured suchthat when the posterior lens is positioned within the eye, the posteriorpositioning means locates the posterior lens in so that it is alignedwith the optical axis of the eye.

In this case, the anterior positioning means may comprise a plurality ofhaptics of equal lengths.

In this way, the haptics are capable of being configured in asymmetrical haptic design when in use such that the image focused ontothe retina by the IOL system is focused at the fovea.

Optionally, the intraocular lens system further includes: an anteriorlens positioning means; and a posterior lens positioning means; whereinthe anterior positioning means is configured such that when the anteriorlens is positioned within the eye, the anterior positioning meanslocates the anterior lens so that it is displaced from alignment withthe optical axis of the eye; and wherein the posterior positioning meansis configured such that when the posterior lens is positioned within theeye, the posterior positioning means locates the posterior lens in sothat it is aligned with the optical axis of the eye.

Optionally, the displacement of the anterior lens is verticaldisplacement.

In this case, the anterior positioning means may comprise a plurality ofhaptics of different lengths. In this way, the haptics are capable ofbeing configured in an asymmetrical haptic design when in use such thatthe anterior lens is displaced from the optical axis of the eye,resulting in an image being focused onto the retina by the IOL system atan area eccentric to the fovea.

Regardless of the positioning means of the anterior lens, the posteriorpositioning means may comprise a plurality of haptics of equal lengths.In this way, the haptics are capable of being configured in asymmetrical haptic design when in use such that the position of theimage focused onto the retina by the IOL system is determined by theposition of the anterior lens relative to the optical axis of the eye.

The displacement of the anterior lens is preferably transverse to theoptical axis of the IOL.

Optionally, the optical axis of the first IOL may be displaced from thatof the second IOL by means of an asymmetric haptic design with onehaptic being shorter than the other. Optionally, this displacement isvertical displacement.

Optionally, the anterior lens and the anterior positioning means is asingle-piece; and/or the posterior lens and the posterior positioningmeans is a single-piece. For example, each lens may be moulded toinclude its haptics.

Preferably, one or both of the intraocular lenses is tinted yellow andthereby configured such that the lens material absorbs light havingwavelengths below 390 nm.

In this way, the transverse chromatic aberration is reduced therebyoptimizing the optics of the system.

Optionally, one or both of the anterior and posterior optics aremodified to include an opaque rim. In this way, vignetting (produced bylarge pupil sizes or decentration) is prevented.

Optionally, optics of the lenses are modified such that a magnifiedimage may be focused on the retina at a wide angle from the fovealcentre.

Optionally, the surfaces of one or both lenses is modified toincorporate a Fresnel prism.

Optionally a third intraocular lens with a surface incorporating adiffractive property is locatable between the first and second lens toincrease the depth of focus of the system.

Optionally, the anterior lens is suitable to be positioned in theanterior chamber of the eye and the posterior lens is suitable to belocated in the ciliary sulcus of the eye. The anterior lens may have adiameter which is no more than 5 mm. Optionally, the anterior lens mayhave a diameter of no less than 4 mm and no more than 5 mm.

Optionally, the anterior lens is suitable to be positioned in theciliary sulcus of the eye and the posterior lens is suitable to bepositioned in the capsular bag of the eye. Again, the anterior lens mayhave a diameter which is no more than 5 mm. Optionally, the anteriorlens may have a diameter of no less than 4 mm and no more than 5 mm.

Preferably at least part of a lens is made from a biocompatiblematerial.

Preferably both lenses are made either partially or entirely from abiocompatible material.

The biocompatible material may be silicone or an acrylic. The materialmay be a rigid material such as polymethylmethacrylate but may be asofter acrylic which may have hydrophobic or hydrophilic properties.

Optionally, the anterior lens is supported by a support device with ahaptic design which enables the optical axis of the anterior lens to befreely moved vertically in relation to that of the posterior lens so asto enable a retinal image to be focused either at the foveal centre orat a range of areas on the retina eccentric to the foveal centre. Thehaptic design may be symmetrical.

The anterior lens and support device may be marked such that alignmentof the lens with a particular mark delivers a set degree of prismaticeffect.

Optionally, the rim of the anterior lens is rendered opaque so as toprevent vignetting.

Optionally, where the anterior lens includes a rim, the rim of the lensis modified to include a holding means, and the points at which it makescontact with the supporting plates are modified to include correspondingholding means such that the rim of the lens is held in position withoutthe need for friction at set points along its axis of movement.

Optionally, the posterior lens is supported by a support device with ahaptic design which permits the optical axis of the posterior lens to befreely moved vertically in relation to that of the anterior lens so asto enable a retinal image to be focused either at the foveal centre orat a range of areas on the retina eccentric to the foveal centre. Again,the haptic design may be symmetrical.

Optionally, the intraocular lens system includes haptics for theanterior lens and/or posterior lens(es) which are angled to enable saidlens(es) to be tilted in a variety of directions relative to the opticalaxis of the eye.

Optionally, the optic of the second IOL (the posterior lens) issupported by a device with a symmetrical haptic design which enables theoptical axis of the posterior optic to be freely moved vertically inrelation to that of the first IOL so as to enable a retinal image to befocused either at the foveal centre or an infinite range of angles awayfrom the foveal centre.

According to a second aspect of the present invention, there is providedan intraocular lens system comprising: an anterior light-convergingintraocular lens for positioning within the eye; and a posteriorlight-diverging intraocular lens for positioning within the eye; whereinthe anterior lens comprises an opaque rim.

Optionally, the anterior lens includes an opaque annulus. This isparticularly useful where the natural pupils of the patient are large asit prevents blurring of the retinal image that may otherwise occur as aresult of light which travels around the outside of the lens.

Where the anterior lens is equipped with an opaque annulus, the annulusmay have an inner diameter of between 5 mm and 7 mm. The annulus may bea separate feature which is connectable to the lens.

One embodiment of the present invention comprises two separate IOLs. Thefirst is a light-converging lens shaped and sized for siting anteriorlyto the second optic in the ciliary sulcus of the eye. The second is aposterior light-diverging lens shaped and sized for siting in thecapsular bag. This embodiment is best employed with the IOLs sited inthese positions but other embodiments allow for siting of thelight-converging lens in the anterior chamber of the eye and thelight-diverging IOL in the ciliary sulcus or both IOLs in the ciliarysulcus. Both IOLs are stabilized in their relative positions by means ofhaptics attached to or continuous with the optic of each lens and theconfiguration provides a magnified image in the manner of a Galileantelescope (in some instances this may be all that is required). However,in order to target a PRL, the haptics attached to the anterior,light-converging lens may be configured asymmetrically in such a waythat one is shorter than the other. This permits displacement of thecentre of the light-converging optic in a plane perpendicular to theoptical axis of the light-diverging lens—thereby conferring a prismaticeffect that allows light to be focused on an area of the maculaeccentric to the fovea. The system allows for free rotation of theanterior IOL in the ciliary sulcus and targeting of other areas of themacula, located at the same angle relative the optic axis of the eye,during subsequent procedures. Furthermore the present invention permitsthe removal of the anterior IOL during subsequent procedures and itsreplacement with an IOL based on the same design but with a differentdioptric power, or haptic lengths, such that light may be focused on apart of the macula located at a different angle or focal point relativeto the optic axis.

The flexible nature of the present invention is made possible byoptimization of the lens surfaces to correct for a range of opticalaberrations. Optimisation of the IOL surfaces is required in the firstinstance because of the high dioptric powers of the optics, since thesedeviate from the thin lens paraxial formula described earlier.Furthermore, an optically unrefined IOL system with a prismatic effectgenerates significant amounts of astigmatism and coma thereby degradingthe quality of the image presented to the patient's fovea or preferredretinal locus. Each IOL of the present invention therefore has at leastone aspherical surface. This allows for a significant improvement in thequality of the image obtained—without it the system would not improve onthe features of the existing systems described above, would confer avery limited benefit and would very likely make an individual's visionworse.

Flexibility is also afforded by the fact that the anterior lens isseparate to the posterior lens and is rotatably movable relative to theposterior lens, i.e. that there is an absence of any coupling betweenthe two lenses of the present invention (thereby permitting freerotation of the anterior IOL or its exchange for a different IOL).However the distance between the two lenses along the optic axis is alsoa critical factor in determining the quality of the retinal image—asmall shift in the position of the lenses relative to one another alongthe optic axis results in the generation of significant refractive errorand degrades the quality of the image presented to the macula. Thecurrent invention overcomes this problem by further manipulation of oneof the two remaining spherical surfaces of the IOLs in the system, themanipulation being aspherization of one of the two remaining sphericalsurfaces thereby inducing spherical aberration to increase the depth offocus and assure both a high quality of retinal image and a significantrange of positioning tolerance. The optics of the system are furtherrefined to take account of the effect of the vertical decentrationbetween both lenses in inducing transverse chromatic aberration—this isdone by applying a yellow tint to one or both of the IOLs included inthe kit. Other modifications to either or both IOLs are included in thedisclosure for the present invention, these variously includerefinements to the optics, such as to reduce vignetting with largerpupils, and changes that permit a wider application of the device. It iscontemplated that the kit will include a range of IOLs of varyingrefractivepowers, surfaces and haptic configurations to permit targetingof PRLs in a wide variety of patients including those with conditionsother than AMD and those with high refractive errors and astigmatism.

DESCRIPTION OF FIGURES

Embodiments of the current invention will be illustrated with referenceto the accompanying drawings of which:

FIG. 1 is a diagrammatic cross-sectional view of an eye

FIG. 2 is a diagrammatic cross-sectional view of an eye featuring anembodiment of the current invention as set out in the present disclosure

FIG. 3 is a top view and side view of the anterior IOL featured as partof the systems illustrated in FIGS. 2 and 6.

FIG. 4 a top view and side view of the posterior IOL featured as part ofthe systems illustrated in FIGS. 2 and 6

FIG. 5 is a side view of the arrangement of the two IOLs with respect toone another as part of the system featured in FIG. 2

FIG. 6 shows a comparison of image quality for a ‘normal design’ and theaspherized design of the present invention that provides for an increasein the tolerance of the system for varying distances between the twooptics

FIG. 7 is a side, oblique and top view of an embodiment of the anteriorIOL

FIG. 8 is a top view and side view of an embodiment of the anterior IOLfeatured in FIGS. 2, 3 and 5

FIG. 9 is a top view and side view of an embodiment of the posterior IOLfeatured in FIGS. 2, 4 and 5

FIG. 10 is a diagrammatic cross-sectional view of an eye featuring anembodiment of the current invention as set out in the present disclosure

It is a key feature of the present invention that the surfaces of eachIOL optic are modelled/configured to minimize optical aberration and toincrease the tolerance of IOL positioning. The surface characteristicsof the intraocular lenses used in the present invention may be describedusing Zernicke polynomials, these are a complete set of orthogonalpolynomials defined on a unit circle which can be used to fit awavefront or surface sag over a circular domain. They efficientlyrepresent common errors such as coma and spherical aberration and aredescribed according to the equation:

z(ρ,θ)=Σ_(i . . . 1) ¹⁵ a _(i) Z _(i)

Where ρ and θ represent the normalized radius and the azimuth anglerespectively and a_(i) is the weighting coefficient for this term.

Table 1 shows the first 15 Zernike terms and the aberrations each termsignifies.

TABLE 1 i Z_(i) (ρ, θ) 1 1 Piston 2 2ρcosθ Tilt x 3 2ρsinθ Tilt y 4{square root over (3)} (2ρ² − 1) Defocus 5 {square root over (6)} (2ρ²sin2θ) Astigmatism 1^(st) order (45°) 6 {square root over (6)} (2ρ²cos2θ) Astigmatism 1^(st) order (0°) 7 {square root over (8)} (3ρ³ −2ρ)sinθ Coma y 8 {square root over (8)} (3ρ³ − 2ρ)cosθ Coma x 9 {squareroot over (8)} (ρ³sinθ) Trifoil 30° 10 {square root over (8)} (ρ³ cosθ)Trifoil 0° 11 {square root over (5)} (6ρ⁴ − 6ρ² + 1) Sphericalaberration 12 {square root over (10)} (4ρ⁴ − 3ρ²)cos2θ Astigmatism2^(nd) order (0°) 13 {square root over (10)} (4ρ⁴ − 3ρ²)sin2θAstigmatism 2^(nd) order (45°) 14 {square root over (10)} (4ρ⁴ cos4θ)Tetrafoil 0° 15 {square root over (10)} (ρ⁴ sin4θ) Tetrafoil 22.5°

For the purposes of promoting a full understanding of the principles ofthe present disclosure, reference will now be made to the Figures. Nolimitation of the scope of the disclosure is intended. Any alterationsand further modifications to the described devices, instruments,methods, and any further application of the principles of the presentdisclosure are fully contemplated as would normally occur to one skilledin the art to which the disclosure relates. In particular, it is fullycontemplated that the features, components, and/or steps described withrespect to one embodiment may be combined with the features, components,and/or steps described with respect to other embodiments of the presentdisclosure.

With reference to FIG. 1, a representation of the human eye incross-section. The eye is bounded by a tough fibrous coat, the sclera 1which is absent anteriorly where it meets the cornea 2. The cornea 2 isa transparent structure that provides the eye with most of its focusingpower and forms the anterior boundary of the anterior chamber 3. Theposterior chamber 4 is separated from the anterior chamber 3 by the iris5. At the anterior periphery of the posterior chamber lies a depressionknown as the ciliary sulcus 6. The iris 5 contains a round, central holeknown as the pupil 7 that allows the passage of light to the naturalcrystalline lens 8. The natural crystalline lens 8 is contained within athin, continuous membrane known as the capsular bag 9 and attached tothe capsular bag 9 are attached numerous fine ligaments known as thezonules 10. At their peripheral extent the zonules 10 are attached tothe ciliary muscle 11. Changes in the shape of the natural crystallinelens 8 are made possible by the action of the ciliary muscle 11 andforces transmitted via the zonules 10 to the capsular bag 9 (an effectknown as accommodation). The natural crystalline lens 8 acts to focuslight rays on the fovea 12, a highly specialised part of the macula 13which in itself is a specialised part of the retina 14 (the lightsensitive tissue at the back of the eye). The retina 14 consists ofmultiple layers that includes a light-sensitive layer of cells known asphotoreceptors. The photoreceptors that facilitate colour vision andhigh-resolution vision (known as cones) are most highly concentrated atthe macula 13 and, most particularly, at the fovea 12—an area that isessential for reading and recognition of faces. It may be seen thatdamage to the fovea 12 and macula 13 may prevent light that has beenfocused at these sites from being detected with a consequent failure ofany image being processed in the brain. Finally, the optical axis 15 isan imaginary line that defines the path along which light propagatesthrough an optical system. For a system such as the eye the optical axis15 passes through the center of curvature of the cornea 2 and naturalcrystalline lens 8 and coincides with the axis of rotational symmetry.

Referring now to both FIGS. 1 and 2. One embodiment of the presentinvention comprises an anterior light-converging IOL 16 located in theciliary sulcus 6 and a posterior light-diverging IOL 17 located in thecapsular bag 18. It should be noted that in this embodiment the capsularbag 18 contains a circular defect anteriorly to facilitate removal ofthe natural crystalline lens or cataract in a manner consistent withcurrent microincisional techniques employed during cataract surgery. Theoptical component of the anterior IOL 16 is maintained in position byhaptics in an asymmetrical configuration such that the first haptic 21is shorter than the second haptic 22—the optical axis of the anteriorlens therefore runs in a path parallel to that of the cornea. The opticof the posterior IOL is maintained in position in the capsular bag bymeans of haptics attached such that the first haptic 19 is the samelength as the second 20—the optical axis of the posterior lens thereforeruns in line with that of the cornea. In this embodiment both optics 16,17 are made of a hydrophobic material, such as soft acrylic polymer(refractive index 1.525; Abbe number 40; visible rangetransmission >95%; ultraviolet light transmission <0.5%), but generallythe optics may be made from any transparent, biocompatible material usedin intraocular lens construction, with calculations for optimisation ofthe optic surfaces (as set out below) revised accordingly. Similarly thehaptics 19, 20, 21, 22 may be may be formed of any suitable polymericmaterial including polymethymethacrylate and/or polypropylene. The IOLsare designed to be foldable to facilitate implantation via a wound inthe eye less than 5 mm in length.

Referring to FIGS. 1, 2, 3, 4, 5 and 6, aspects of the IOLs and theirarrangement are discussed in more detail. FIG. 2 shows the anteriorlight-converging IOL in crosssection 26 and from the top 27. Theanterior converging IOL consists of a lightconverging optic of athickness 28, a diameter 29 and a dioptric power such that inconjunction with the posterior IOL, light may be focused on a region ofthe macula to provide a retinal image of a specific magnification. Toachieve a retinal image of sufficient quality to benefit an individualwith poor central vision, the optical design of the first lens isoptimized such that it consists of a spherical anterior surface 30 andan aspheric posterior surface 31. The anterior surface of the first lensis a standard spherical surface. The posterior surface of the first lensis a rotationally symmetric polynomial aspheric surface for which thesurface sag (z co-ordinate) as a function of the radial coordinate r canbe given by:

$z = {\frac{{cr}^{2}}{1 + \sqrt{1 - {\left( {1 + k} \right)c^{2}r^{2}}}} + {\alpha_{1}r^{2}} + {\alpha_{2}r^{4}} + {\alpha_{3}r^{6}}}$

Wherein,

i) c is the inverse of the radius of curvature R: c=1/Rii) k is the conical constant (with a value ranging between −1 and 0iii) a is an aspheric polynomial coefficient, additional to the conicalconstant

So that areas of macula at a set angle of deviation from the centre ofthe fovea may be targeted, two haptics are attached to or continuouswith the anterior optic such that the first haptic 32 is longer than thesecond haptic 33. The optic is therefore sited further from the point atwhich the haptic is designed to make contact with the eye 6 on one side34 than on the other 35. It should be noted that in this embodiment bothhaptics are angled anteriorly from the point at which they emerge fromthe optic in such a way that the optic is sited in a plane that liesposterior to that of the ciliary sulcus—in this way the anterior surfaceof the anterior IOL remains clear of the iris 5. With reference to FIG.4, the posterior light-diverging IOL is shown in cross-section 36 andfrom the top 37. The posterior light-diverging IOL consists of alight-diverging optic of a central thickness 38, diameter 39 anddioptric power such that in conjunction with the anterior IOL, light maybe focused on a region of the macula to provide a retinal image ofspecific magnification. Again, to achieve a retinal image of sufficientquality with this configuration the optical design of the posterioroptic is optimised such that it consists of a rotationally symmetricpolynomial aspheric anterior surface 40 and a standard conic posteriorsurface 41. For the aspheric anterior surface 40, the surface is arotationally symmetric polynomial aspheric surface for which the surfacesag z as a function of the radial coordinate r can be given byexpression:

$z = {\frac{{cr}^{2}}{1 + \sqrt{1 - {\left( {1 + k} \right)c^{2}r^{2}}}} + {\alpha_{1}r^{2}} + {\alpha_{2}r^{4}} + {\alpha_{3}r^{6}}}$

The sag (z coordinate) of the posterior surface of the second lens 41can be given by the expression:

$z = \frac{{cr}^{2}}{1 + \sqrt{1 - {\left( {1 + k} \right)c^{2}r^{2}}}}$

Attached to or continuous with the posterior optic are two haptics 42,43 of equal length 44, 45. The haptics are designed such that theposterior IOL may be sited in the capsular bag. It should be noted thatin order to achieve a maximal distance from the anterior IOL it may benecessary to angle the haptics 42, 43 attached to the posterior IOL suchthat the optic lies in a plane posterior to the site where the hapticsmake contact with the periphery of the capsular bag 18. With referenceto FIG. 5, that shows a cross-section of the arrangement of the anteriorIOL in relation to the posterior IOL: The IOLs are arranged in the eyesuch that the anterior light-converging IOL 46 is sited at a fixeddistance (in a direction parallel to the optical axes) from theposterior light-diverging IOL 47 resulting in a magnification of theretinal image of 1.2 to 1.4.

Since even a small deviation from the intended axial positioning of thetwo implants relative to one another could produce a significantrefractive error and degradation of the image presented at the retina,the current invention increases the tolerance of the system forsub-optimal implant axial positioning by aspherizing one of the tworemaining spherical surfaces in the system 52, 53 to add sphericalaberration and increase the depth of focus. The precise amount of addedspherical aberration is determined to assure both a good enough qualityof retinal image and a significant range of positioning tolerance. Thisfeature of the present invention ensures that it is capable ofdelivering a high quality of retinal image whilst accommodatingvariations in the practice of individual surgeons and alterations in theanatomy of the eye during the early and late post-operative periods.

The benefits of added spherical aberration, in increasing the toleranceof IOL positioning in the present invention are shown in FIG. 6.

The optics of the system are further optimised to take account oftransverse chromatic aberration induced by the vertical displacement ofthe implants relative to one another 51, this is achieved by adding ayellow tint to the implants during the manufacturing process. Theaddition of a yellow tint to the IOLs also confers the added benefit ofmacular protection from ultraviolet radiation.

With reference to Table 1, it can be seen that the surfaces of theoptics of the IOLs of the present invention may be further optimised bythe addition of values for Zernicke polynomials, besides those forspherical aberration. The surfaces may be expressed as a linearcombination Zernicke polynomials including those for tilt, defocus,astigmatism, and coma, such that optical aberrations for individualpatients are minimised. Consequent remodeling of the lenses means thatat least one lens design parameter is changed—this may include theanterior surface shape and central radius and the posterior surfaceshape and central radius—and IOLs may be selected from a kit of lensesto achieve the desired effect.

The asymmetric haptic lengths of the anterior light-converging IOLgenerate a vertical displacement 51 of its optic axis 49 from that ofthe light-diverging posterior IOL (and cornea) 50. With reference toFIG. 2, this displacement produces a deviation of path of light 24 suchthat a magnified retinal image is focused on an area of healthy macula25 beyond the foveal centre. The materials, biomechanical properties,lengths and shapes of the haptics and the materials, surfaces, sizes andbiomechanical properties of the anterior and posterior optics may bemodified to achieve the desired displacement and corresponding retinalimage (the haptics may form part of a single piece anterior or posteriorIOL for example). It is contemplated that varying degrees ofdisplacement may be achieved by selection of an anteriorlight-converging IOL of differing haptic lengths such that a range ofangles extending from the centre of the fovea to >3 degrees (in theretinal plane), may be targeted, if necessary by using anterior segmentimaging to ensure haptic lengths are appropriate for the size of anindividual's ciliary sulcus or other location. Alternatively, FIG. 7shows an embodiment of the anterior light-diverging IOL shown from theside 54, obliquely 55 and from the top 56. In this embodiment theanterior light-converging optic 57 has an additional, optically neutralrim 58 (or an opaque rim to prevent vignetting) that permits the opticto be slid, with the application of force by the surgeon, between twoplates made of biocompatible material 59, 60. The plates 59, 60 arejoined by supporting posts superiorly 61 and inferiorly 62 with, angled,symmetrical haptics 63, 64, inserting into one of the two platessupporting the optic. This arrangement permits the optic to be slid froma neutral position vertically in a plane perpendicular to the opticalaxis as indicated by the arrow 65, thereby conferring a range ofprismatic effects without having to introduce IOLs with differing hapticlengths. The IOL may be marked in such a way that alignment of the opticwith specific markings delivers a set amount of prismatic effect anddeviation of the image from the foveal centre. Similarly the surface ofthe optic and its points of contact with the supporting plates may bemodified such that the optic may held in set positions along its axis ofmovement. It is further contemplated that a range of anterior andcorresponding posterior implants, consisting of a range of dioptricpowers, optical surfaces, optic tints and haptic configurations may beincluded in the kit to facilitate targeting of the PRL in individualpatients with a wide range of refractive errors (this includes toricoptics to correct for high astigmatism). It will also be appreciatedthat rotation of the anterior light converging IOL around its opticalaxis, whilst keeping it in the same plane as the light-divergingposterior IOL, confers the ability to target a full range of locationsin the macula at the set angle prescribed by the vertical displacementbetween the two IOLs (that is to say that the azimuth of the focal pointof the system is fully adjustable). To facilitate this, an opticallyneutral mark may be included on the anterior light-converging optic sothat its degree of rotation in relation to the eye can be determinedwithout reference to the position of its haptics.

Referring now to FIG. 8 which shows a version of the anteriorlight-converging IOL in cross-section 66 and from the top 67. It iscontemplated that with the current invention there is risk of visuallysignificant vignetting occurring with larger pupil sizes, particularlywhere levels of vertical decentration between the anterior and posteriorIOLs are high. A version of the anterior light-converging IOL designedto prevent such vignetting is shown 66, 67. The diameter of the optic isincreased in this embodiment 68 with an added rim 69 rendered opaque bythe application of a biocompatible and stable opaque paint to itssurface 70.

Alternatively an opaque, rim may be located on the surface of the optic,for example bonded to the optic as originally conceived to create thesame effect. The rim is of sufficient width to prevent vignetting withlarger pupils and/or at high levels of vertical displacement of theIOLs. The refractive part of the optic remains unaffected and thehaptics 71, 72, which may be of equal or differing lengths, insert intothe optic as previously described. With reference to FIG. 9, which showsa version of the posterior light-diverging IOL in cross-section 73 andfrom the top 74; the same, or a similar, effect may be achieved byincreasing the diameter of the posterior optic 75 to include a rim 76that may be opaque and bonded to the optic or, as shown in theillustration, rendered opaque by means of a biocompatible and stableopaque paint applied to its surface 77 (the configuration of the hapticsremaining unchanged 78, 79).

In a further embodiment (not shown) the opaque rim may be located withinpart of the optic body.

Reference to FIGS. 5 and 9 may now be made. FIG. 10 shows a secondembodiment of the current invention in a cross-section of the eye. Thisembodiment is the same as the first except that the verticaldisplacement of the IOLs relative to one another 51 is absent (that isto say that optical axes of the anterior 80 and posterior 81 optics arealigned with that of the cornea). To achieve this, the haptics of thefirst optic are of equal length 82, 83. This focuses light entering theeye 84 in such a way that a magnified retinal image is centred on thefovea 85. Alternatively the embodiment as shown in FIG. 7 allows forpositioning of the anterior optic such that its optical axis is in linewith that of the posterior lens such that only magnification and noprismatic effect is generated. It is contemplated that in conditionssuch as amblyopia, where the overall structure of the fovea and macularemain intact, that it will not be necessary to deviate the path oflight in the eye to target areas of the macula outside of the fovea. Inthis embodiment the haptics of the anterior light-converging IOL are ofequal length and yellow tinting of the optics is not required in theabsence of transverse chromatic aberration. It is further contemplatedthat a range of optics of varying dioptric powers, sizes and materialsmay be used, as in the first embodiment, to facilitate focusing of themagnified image on the fovea.

Although the invention is described in the preferred embodimentsillustrated in the Figures attached, no restriction is intended by this.The design and configuration of the optical surfaces, includingapplication of a tint to refine optical properties, are consideredintegral to the present invention and may be applied in a variety ofcircumstances. For example it is contemplated that an arrangement of theIOLs may include positioning of the anterior light-converging IOL in theanterior chamber 3 and the posterior light-diverging IOL in the ciliarysulcus 6 or both IOLs in the ciliary sulcus with revision of the opticalsurfaces, IOL dioptric powers and haptic designs accordingly. Similarly,it is contemplated that the asymmetric haptic design of the anteriorlight-converging IOL may be applied to the posterior light-diverging IOLso that the optics produce a combined prismatic effect.

Further embodiments (not shown) include the application of diffractivesurfaces to one optic or both optics to permit a range of focal pointsin the eye (and consequently uncorrected distance and near vision); theapplication of a Fresnel prism to one or both optics to achieve aprismatic effect and targeting of the PRL—or the introduction of a thirdoptic with one of the aforementioned characteristics, to either ananterior chamber, the ciliary sulcus or the capsular bag.

Again, whilst reference to use of the present invention in subjects withAMD is made, no restriction in terms of its use is intended. It iscontemplated that the present invention will be used in a wide varietyof clinical scenarios with or without displacement of the optics toachieve targeting of areas of the macula eccentric to fixation and witha range of magnification and refractive capabilities. The presentinvention is designed for insertion into the eye via a small (5 mm)incision with or without use of a cartridge injector, an approachconsistent with its use in the context of surgical techniques employedduring natural crystalline lens or cataract extraction. As such it isexpected that the present invention may be used in combination withnatural crystalline lens extraction or at the time of cataract surgeryor, if necessary, subsequent to cataract surgery/lens extraction (withits application—together with any necessary modifications to the opticsurfaces, haptic design, optic materials and optic dioptric power—inaddition to or instead of pre-existing implants in the eye).

In keeping with this approach, a range of monofocal IOLs may be providedthat is designed for use in cases where the present invention is notindicated at initial surgery, but where the natural crystalline lens isremoved and the patient wishes to retain the potential to use thepresent invention at a later date. Under these circumstances, the opticsof the monofocal IOL implanted at the first operation will be optimisedfor use in conjunction with the present invention should this berequired in the event that the patient develops a macular disease.

CLAUSES

In addition to the description above, optional features of the inventionare described in the clauses below:

Clause 2. An intraocular lens system according to Clause 1 in which oneor both of the intraocular lenses is tinted a particular colour tooptimize the optics of the system by reducing transverse chromaticaberration and to protect the macula from excessive ultravioletradiation exposure.

Clause 3. An intraocular lens system according to Clause 2 whereby thedistance between the optics and the degree of vertical displacement ofthe optical axis of the first lens may be varied together with thedioptric powers of the lenses and their optical surfaces such that lightentering the eye may be focused on an area of the retina outside thecentre of the fovea.

Clause 4. The system of Clause 3 where asphericity is added to one ofthe two remaining spherical surfaces of the two optics to increase therange of depth of focus thereby increasing the tolerance of thepositioning of the lenses in the system.

Clause 5. A system of Clause 4 whereby either the anterior or posterioroptics (or both) are modified to include an opaque rim such thatvignetting (produced by large pupil sizes or decentration) is prevented.

Clause 6. The system of Clause 4 whereby the optics of the IOLs aremodified such that a magnified image may be focused on the retina at awide angle from the foveal centre.

Clause 7. A system according to Clause 4 whereby the surfaces of one orboth optics are modified to provide a range of accommodation.

Clause 8. A system according to Clause 4 whereby the surfaces of one orboth optics is modified to incorporate a Fresnel prism.

Clause 9. A system according to Clause 4 whereby a third intraocularlens with a surface incorporating a Fresnel prism may be introducedbetween the first and second lens to provide a prismatic effect.

Clause 10. A system according to Clause 4 where a third intraocular lenswith a surface incorporating a diffractive property may be introducedbetween the first and second lens to increase the depth of focus of thesystem.

Clause 11. A system according to Clause 4 where the anterior IOL ispositioned in the anterior chamber of the eye and the posterior IOL inthe ciliary sulcus of the eye.

Clause 12. A system according to Clause 4 where the anterior IOL ispositioned in the ciliary sulcus of the eye and the posterior IOL ispositioned in the capsular bag of the eye.

Clause 13. A system according to Clause 4 where the IOLs aresingle-piece (moulded to include the haptics).

Clause 14. A system according to Clause 4 where the optics of the IOLsor the IOLs in entirety are made from a biocompatible material such assilicone or polymethylmethacrylate.

Clause 15. A system according to Clause 4 whereby the optic of the firstIOL is displaced vertically from that of the second IOL by means of anasymmetric haptic design with one haptic being shorter than the other.

Clause 16. A system according to Clause 4 where the optical axis of thefirst IOL is in line with that of the second IOL to focus an image atthe foveal centre.

Clause 17. A system according to Clause 4 where the optic of the firstIOL is supported by a device with a symmetrical haptic design whichpermits the optical axis of the anterior optic to be freely movedvertically in relation to that of the second IOL so as to enable aretinal image to be focused either at the foveal centre or an infiniterange of angles away from the foveal centre.

Clause 18. A system according to Clause 17 where the IOL optic andsupporting device are marked such that alignment of the optic with aparticular mark delivers a set degree of prismatic effect.

Clause 19. A system according to Clause 17 where the rim of the optic isrendered opaque so as to prevent vignetting.

Clause 20. A system according to Clause 17 where the rim of the optic ismodified and the points at which it makes contact with the supportingplates are modified such that it is held in position without the needfor friction at set points along its axis of movement.

Clause 21. A system according to Clause 17 where the haptics are angledto enable the optic to be tilted in a variety of directions.

Clause 22. A system according to Clause 1 that may be used incombination with a monofocal IOL sited within the capsular bag

Clause 23. An IOL for implantation in the capsular bag, followingcataract surgery or removal of the natural crystalline lens, that isoptimized in such a way that it may be retained in the capsular bag at asubsequent implantation of the system according to claim 4.

Clause 24. An IOL according to claim 20 with haptics angled in such thatit may be sited in the posterior aspect of the capsular bag, therebypermitting introduction of the system according to claim 4 anteriorly.

Clause 25. A system according to claim 4 where the optic of the secondIOL is supported by a device with a symmetrical haptic design whichpermits the optical axis of the posterior optic to be freely movedvertically in relation to that of the first IOL so as to enable aretinal image to be focused either at the foveal centre or an infiniterange of angles away from the foveal centre.

A wide range of modification and substitution is contemplated withregards to the present disclosure, and the illustrations provided arenot intended to restrict the design of the present invention or limitthe applications of its use. Furthermore it is intended that a varietyof permutations of the present invention may be created by incorporatingthe various properties as laid out in the Claims attached.

1. An intraocular lens system comprising: an anterior light-convergingintraocular lens for positioning within the eye, the anterior lenshaving an anterior surface and a posterior surface; and a posteriorlight-diverging intraocular lens for positioning within the eyeposterior to the anterior lens, the posterior lens having an anteriorsurface and a posterior surface; wherein the posterior lens is separateto the anterior lens; and wherein at least one of the surfaces of theanterior lens or surfaces of the posterior lens is a modified surfacewhich includes a surface aberration which increases the depth of focusof the lens.
 2. An intraocular lens system according to claim 1, whereinthe surface aberration includes a spherical aberration.
 3. Anintraocular lens system according to claim 2, wherein the modifiedsurface is a rotationally symmetric polynomial surface.
 4. Anintraocular lens according to any one of the preceding claims, whereinthe surface aberration includes an aberration of at least 4^(th) order.5. An intraocular lens according to any one of the preceding claims,wherein the surface aberration includes an aberration of no more than6^(th) order.
 6. An intraocular lens according to any one of claims 3 to5, wherein the surface sag (z coordinate) of the modified surface isgiven by:$z = {\frac{{cr}^{2}}{1 + \sqrt{1 - {\left( {1 + k} \right)c^{2}r^{2}}}} + {\alpha_{1}r^{2}} + {\alpha_{2}r^{4}} + {\alpha_{3}{r^{6}.}}}$7. The intraocular lens according to any one of the preceding claims,wherein the modified surface includes a second aberration, the secondaberration being a Zernike polynomial for any one of: tilt, defocus,astigmatism, or coma.
 8. An intraocular lens system according to any oneof the preceding claims comprising a first and a second modifiedsurface.
 9. An intraocular lens system according to claim 8, whereinboth the anterior lens and the posterior lens each include a modifiedsurface.
 10. An intraocular lens system according to claim 9, whereinthe posterior surface of the anterior lens and the anterior surface ofthe posterior lens are both modified surfaces.
 11. An intraocular lenssystem according to any one of the preceding claims, further comprising:an anterior lens positioning means; and a posterior lens positioningmeans; wherein the anterior positioning means is configured such thatwhen the anterior lens is positioned within the eye, the anteriorpositioning means locates the anterior lens so that it is aligned withthe optical axis of the eye; and wherein the posterior positioning meansis configured such that when the posterior lens is positioned within theeye, the posterior positioning means locates the posterior lens in sothat it is aligned with the optical axis of the eye.
 12. An intraocularlens system according to claim 11, wherein the anterior positioningmeans comprises a plurality of haptics of equal lengths.
 13. Anintraocular lens system according to any one of claims 1 to 11, furthercomprising: an anterior lens positioning means; and a posterior lenspositioning means; wherein the anterior positioning means is configuredsuch that when the anterior lens is positioned within the eye, theanterior positioning means locates the anterior lens so that it isdisplaced from alignment with the optical axis of the eye; and whereinthe posterior positioning means is configured such that when theposterior lens is positioned within the eye, the posterior positioningmeans locates the posterior lens in so that it is aligned with theoptical axis of the eye.
 14. An intraocular lens system according toclaim 13, wherein the anterior positioning means comprises a pluralityof haptics of different lengths.
 15. An intraocular lens systemaccording to any one of claims 11 to 14, wherein the anterior lens andthe anterior positioning means is a single-piece; and/or Wherein theposterior lens and the posterior positioning means is a single-piece.16. An intraocular lens system according to any one of the precedingclaims, wherein one or both of the intraocular lenses is tinted yellow.17. An intraocular lens system of any one of the preceding claimswherein one or both of the anterior and posterior optics are modified toinclude an opaque rim.
 18. An intraocular lens system of any one of thepreceding claims, wherein optics of the lenses are modified such that amagnified image may be focused on the retina at a wide angle from thefoveal centre.
 19. An intraocular lens system according to any one ofthe preceding claims wherein the surfaces of one or both lenses ismodified to incorporate a Fresnel prism.
 20. An intraocular lens systemaccording to any one of the preceding claims wherein a third intraocularlens with a surface incorporating a Fresnel prism is locatable betweenthe first and second lens to provide a prismatic effect.
 21. Anintraocular lens system according to any one of claims 1 to 20, whereina third intraocular lens with a surface incorporating a diffractiveproperty is locatable between the first and second lens to increase thedepth of focus of the system.
 22. An intraocular lens system accordingto any one of the preceding claims, where the anterior lens is suitableto be positioned in the anterior chamber of the eye and the posteriorlens is suitable to be located in the ciliary sulcus of the eye.
 23. Anintraocular lens system according to any one of claims 1 to 22 where theanterior lens is suitable to be positioned in the ciliary sulcus of theeye and the posterior lens is suitable to be positioned in the capsularbag of the eye.
 24. An intraocular lens system according to any one ofthe preceding claims, wherein at least part of a lens is made from abiocompatible material.
 25. An intraocular lens system according toclaim 24, wherein the biocompatible material is silicone orpolymethylmethacrylate.
 26. An intraocular lens system according to anyone of claim 1 to claim 10, wherein the anterior lens is supported by asupport device with a symmetrical haptic design which enables theoptical axis of the anterior lens to be freely moved vertically inrelation to that of the posterior lens so as to enable a retinal imageto be focused either at the foveal centre or at a range of areas on theretina eccentric to the foveal centre.
 27. An intraocular lens systemaccording to claim 26 wherein the anterior lens and support device aremarked such that alignment of the lens with a particular mark delivers aset degree of prismatic effect.
 28. An intraocular lens system accordingto claim 26, Wherein the anterior lens includes a rim; and wherein therim of the lens is modified and the points at which it makes contactwith the supporting plates are modified such that it is held in positionwithout the need for friction at set points along its axis of movement.29. An intraocular lens system according to any one of claim 1 to claim10, wherein the posterior lens is supported by a support device with asymmetrical haptic design which permits the optical axis of theposterior lens to be freely moved vertically in relation to that of theanterior lens so as to enable a retinal image to be focused either atthe foveal centre or at a range of areas on the retina eccentric to thefoveal centre.
 30. An intraocular lens system according to any one ofthe preceding claims, comprising haptics for the anterior lens and/orposterior lens(es) which are angled to enable said lens(es) to be tiltedin a variety of directions relative to the optical axis of the eye. 31.A system according to claim 4 where the optic of the second IOL issupported by a device with a symmetrical haptic design which enables theoptical axis of the posterior optic to be freely moved vertically inrelation to that of the first IOL so as to enable a retinal image to befocused either at the foveal centre or an infinite range of angles awayfrom the foveal centre.
 32. An intraocular lens system comprising: ananterior light-converging intraocular lens for positioning within theeye; and a posterior light-diverging intraocular lens for positioningwithin the eye; wherein the anterior lens comprises an opaque rim.